The present invention relates to new nanocomposites based on nanoscale carbon fibers and tubes modified with hyperbranched ether-ketone polymers on the surfaces and their methods of preparation.
One-dimensional, carbon-based, nano-structured materials are generally divided into three categories based on their diameter dimensions: (i) single-wall carbon nanotubes or SWNT (0.7-3 nm); (ii) multi-wall carbon nanotubes or MWNT (2-20 nm); (iii) carbon nanofibers or CNF (40-100 nm). While the length of vapor grown carbon nanofiber (VGCNF) ranges 30-100 μm, it is difficult to determine the lengths of SWNT and MWNT because of their strong proclivity to aggregate (to form “ropes”) but they are generally considered to be two-orders of magnitude shorter than CNF.
Because of the numerous technological opportunities that their extraordinary thermal, electrical, mechanical, and optical properties could lead to, they have been receiving widespread attention in the advanced materials research community in recent years. To take advantage of their predicted properties, these nanomaterials are being actively investigated with respect to their structural reinforcement, energy/electron transport or storage capabilities, and interactions with electromagnetic waves, as well as the efficient ways to transfer their outstanding properties to the polymeric matrices. A common goal is to make the resulting polymer nanocomposites for advanced applications that are affordable, lightweight and multi-functional. Several studies have been performed on CNT or VGCNF and reported their reinforcement in various thermoplastics and thermoset matrices. As an approach to achieving a good dispersion of single-wall carbon nanotube (SWNT) in a high performance polymer, in-situ polymerization of polybenzoxazole (PBO) with SWNT in polyphosphoric acid (PPA) at 190° C. has been reported recently. Additionally, great strides have been achieved in the functionalization of SWNT to impart solubility and provide more processing options. Various in-situ polymerization methods in grafting hyperbranched polymers to or from the surfaces of carbon nanofibers and carbon nanotubes have been reported in the literature: (a) atom-transfer radical polymerization (ATRP); (b) ring-opening polymerization; (c) self-condensing vinyl polymerization (SCVP); (d) polycondensation. In a most recent example, SWNT was grafted with poly(aminoamine)-type dendrimers using a divergent methodology. In all cases, (a) the CNF/CNT surfaces were prefunctionalized with appropriate functional groups (e.g. initiators) for the subsequent polymerization processes; (b) either aliphatic or partially aliphatic hyperbranched polymers were resulted. In this invention, no such prefunctionalization was required, and the resulting hyperbranched poly(ether-ketone) is wholly aromatic, which will allow higher use temperatures.
Accordingly, it is an object of the present invention to provide a process to attach a carboxylic acid-terminated hyperbranched poly(ether-ketone) onto the surfaces of nanoscale carbon fibers and tubes.
It is another object of this invention to provide functionalized nanoscale carbon fibers and tubes via end-group functionality conversion of the carboxylic acid-terminated hyperbranched polymer.
Other objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.